“…The crystal structures of the HM and LM (Orth II) phases are depicted in Figure . , The cell parameters and other structural features are summarized in Table . 2 Crystal structure of the HM and LM phases of petroselinic acid.…”
Section: Polymorphism Of Petroselinic Acidmentioning
confidence: 99%
“…For the B and E forms of stearic acid, single crystals of Mon are easier to obtain than those of Orth II. Recently we found that on the crystallization of the E form single crystals start to grow as Mon, and then the overgrowth of Orth II took place on the flat (001) face of the crystals, even though the Orth II region is predominant in the late stages. − So we expected that single crystals of the LM phase would be Mon in the beginning of crystallization.…”
Section: Introductionmentioning
confidence: 98%
“…Petroselinic acid occupies a specific position in chemical structure among naturally occurring cis-monounsaturated fatty acids whose acyl hydrocarbon chain is divided into two segments by cis-CC double bond; the methyl-terminal chain is about two times longer than the carboxyl-terminal one and contains an even-number of carbon atoms in contrast to the odd-number of carbon atoms in most monounsaturated fatty acids. In previous study we found that this chemical structural feature has a large influence on physicochemical properties and polymorphism. − (1) Petroselinic acid melts at appreciably higher temperatures (more than 10 °C) than oleic acid ( cis -9-octadecenoic acid) and asclepic acid ( cis -11-octadecenoic acid), consisting of the same number of carbon atoms. (2) There is no reversible solid-state phase transition that has been found in many cis-monoenoic acids: oleic acid, erucic acid, palmitoleic acid, and so on.…”
Polytypism and solid-state phase transitions of petroselinic acid (cis-6-octadecenoic acid) have been investigated with microscopic observation and micro-FT-IR spectroscopy. Polytypism was confirmed for the low-melting (LM) phase. In solution crystallization of the LM phase, polytypic transformation from a single-layered polytype to a double-layered one was observed. The LM phase performs a solid-state phase transition to the high-melting phase through two mechanisms. One mechanism involves the thermally induced nucleation and growth of the product phase, which is dominant upon a slow heating process. The other mechanism can be regarded as a martensitic transition, where rapid cooperative molecular displacements are initiated by a local stress. The martensitic transition occurs when a single crystal of the single-layered polytype suffers rapid heating or mechanical stress. However, no martensitic transition was observed for the double-layered polytype. The difference in transition behavior between the two polytypes was interpreted on the basis of crystal structures.
“…The crystal structures of the HM and LM (Orth II) phases are depicted in Figure . , The cell parameters and other structural features are summarized in Table . 2 Crystal structure of the HM and LM phases of petroselinic acid.…”
Section: Polymorphism Of Petroselinic Acidmentioning
confidence: 99%
“…For the B and E forms of stearic acid, single crystals of Mon are easier to obtain than those of Orth II. Recently we found that on the crystallization of the E form single crystals start to grow as Mon, and then the overgrowth of Orth II took place on the flat (001) face of the crystals, even though the Orth II region is predominant in the late stages. − So we expected that single crystals of the LM phase would be Mon in the beginning of crystallization.…”
Section: Introductionmentioning
confidence: 98%
“…Petroselinic acid occupies a specific position in chemical structure among naturally occurring cis-monounsaturated fatty acids whose acyl hydrocarbon chain is divided into two segments by cis-CC double bond; the methyl-terminal chain is about two times longer than the carboxyl-terminal one and contains an even-number of carbon atoms in contrast to the odd-number of carbon atoms in most monounsaturated fatty acids. In previous study we found that this chemical structural feature has a large influence on physicochemical properties and polymorphism. − (1) Petroselinic acid melts at appreciably higher temperatures (more than 10 °C) than oleic acid ( cis -9-octadecenoic acid) and asclepic acid ( cis -11-octadecenoic acid), consisting of the same number of carbon atoms. (2) There is no reversible solid-state phase transition that has been found in many cis-monoenoic acids: oleic acid, erucic acid, palmitoleic acid, and so on.…”
Polytypism and solid-state phase transitions of petroselinic acid (cis-6-octadecenoic acid) have been investigated with microscopic observation and micro-FT-IR spectroscopy. Polytypism was confirmed for the low-melting (LM) phase. In solution crystallization of the LM phase, polytypic transformation from a single-layered polytype to a double-layered one was observed. The LM phase performs a solid-state phase transition to the high-melting phase through two mechanisms. One mechanism involves the thermally induced nucleation and growth of the product phase, which is dominant upon a slow heating process. The other mechanism can be regarded as a martensitic transition, where rapid cooperative molecular displacements are initiated by a local stress. The martensitic transition occurs when a single crystal of the single-layered polytype suffers rapid heating or mechanical stress. However, no martensitic transition was observed for the double-layered polytype. The difference in transition behavior between the two polytypes was interpreted on the basis of crystal structures.
“…The a and c phases of oleic acid were also found in erucic (C 22:1 , 13-cis) [17,18], gondoic (C 20:1 , 11-cis) [1], asclepic (C 18:1 , 11-cis) [19,20], and palmitoleic (C 16:1 , 9-cis) acids [18], all of which have a cis double bond at odd-numbered carbon positions. Peteroselinic acid (C 18:1 , 6-cis), having a cis double bond at even-numbered carbon positions, has two forms (LM and HM) [21][22][23][24], whose polymorphic structures are quite different from those of the other cis-monounsaturated fatty acids but rather similar to those of saturated fatty acids [21]. In elaidic acid (C 18:1 , 9-trans), which is a trans isomer of oleic acid, Ueno et al reported one crystal form [25].…”
Thermal properties, powder X-ray diffraction patterns and FT-IR absorption spectra of crystals of two isomers of conjugated linoleic acid (CLA), 9-cis, 11-trans-CLA (c9t11), 10-trans, 12-cis-CLA (t10c12) were examined. To search for polymorphic modifications, we carefully performed crystallization from melt and solution phases, and isolated one type of crystalline form in c9t11 and t10c12. The melting temperature (T m ) was 14.9°C, enthalpy of fusion (DH) was 38.7 kJ/mol, and entropy of fusion (DS) was 134 J/mol K for c9t11, and T m = 19.8°C, DH = 35.6 kJ/mol and DS = 122 J/mol K for t10c12. The X-ray diffraction and FT-IR measurements indicated O \ subcell packing in the crystals of c9t11 and t10c12, and long spacing values of 4.22 nm for c9t11 and 3.88 nm for t10c12. The unique molecular structures of the two isomers of CLA are discussed in comparison to the polymorphism of oleic acid, petroselinic acid, elaidic acid and linoleic acid, all of which are unsaturated fatty acids having the same carbon number of 18 as that of the two CLA isomers.
“…Hence, it must be of the highest importance to elucidate molecular-level understanding of structure-function relationships of the unsaturated fatty acids. The authors have studied thermal and structural properties of principal unsaturated acids over the past 10 yr, dealing with single phases of oleic acid [cis-C 18:1 ∆9ω9 (OA)] (2)(3)(4)(5), erucic acid [cis-C 22:1 ∆13ω9 (ERA)] (6-10), petroselinic acid [cis-C 18:1 ∆6ω12 (PSA)] (11)(12)(13), asclepic acid [cis-C 18:1 ∆11ω7 (APA)] (7,14), palmitoleic acid [cis-C 16 (19). Table 1 summarizes the molecular properties of six unsaturated fatty acids involving trans-type elaidic acid, together with thermal data of phase transitions.…”
Molecular properties of polymorphic forms of gondoic acid [cis-C 20:1 ∆11ω9 (GOA)] have been studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), optical microscopy, and Raman scattering, in comparison to those of six principal unsaturated fatty acids: oleic acid [cis-C 18:1 ∆9ω9 (OA)], erucic acid [cis-C 22:1 ∆13ω9 (ERA)], petroselinic acid [cis-C 18:1 ∆6ω12 (PSA)], asclepic acid [cis-C 18:1 ∆11ω7 (APA)], palmitoleic acid [cis-C 16:1 ∆9ω7 (POA)], and elaidic acid [trans-C 18:1 ∆9ω9 (ELA)]. In addition, phase behavior of binary mixtures of GOA and APA and OA was examined by XRD and DSC. The polymorphic structures of GOA are quite similar to those of APA, ERA, POA, and partly to OA. In particular, DSC and Raman scattering studies have shown that gondoic acid exhibits conformational disordering on heating at the ω-chain, a chain segment between the double bond and CH 3 group, as a transition from alltrans (γ form) to gauche-rich (α form) conformations. A miscible mixing phase was observed in the mixture of GOA and APA, yet eutectic phases were observed in the GOA and OA mixtures. This is a remarkable contrast because the binary mixture systems of varying combinations of cis-unsaturated fatty acids examined so far exhibited either eutectic nature or molecular compound formation. It is expected that specific molecular interactions between GOA and APA that originate from the equivalence of the length of the ∆-chain, the chain segment between the cis-double bond and COOH group, and also from the presence of the γ-α order-disorder transformation would be operating to form the miscible mixing phase. JAOCS 74, 1153JAOCS 74, -1159JAOCS 74, (1997.KEY WORDS: Asclepic acid, differential scanning calorimetry, gondoic acid, oleic acid, phase behavior of binary mixtures, polymorphism in unsaturated fatty acids, X-ray diffraction.
FIG. 1.A molecular model of γ-α transformation observed in oleic acid, erucic acid, asclepic acid, and palmitoleic acid.
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